1. Field of the Invention
The present invention relates to an organic wastewater purification system capable of generating swirling flow (or vortex) in multiple vertical compartments of an aeration tank while circulating wastewater vertically in the tank and, more particularly, to a system for purification of organic wastewater that generates swirling flow in respective compartments while flowing the wastewater up and down and in a zig-zag pattern in respective wastewater treatment blocks in the system, so as to prolong contact time between air and the wastewater, in turn remarkably improving wastewater treatment efficiency and, as a result, enabling decrease in the size of an aeration tank.
2. Description of the Related Art
Most contaminants in sewage contain organic matter and nutrients consisting mainly of nitrogen and phosphorous. As such, a variety of attempts have been made to develop a wastewater purification system operating based upon removal of nitrogen and phosphorus.
Most conventional processes for removal of biological nitrogen, phosphorous, or the like are executed using different types of reactors, for example: an oxic reactor (commonly referred to as ‘aeration tank’) for nitrification and intake of excess phosphorous; an anoxic reactor for de-nitrification; an anaerobic reactor for discharging phosphorous, and so forth.
Such an aeration tank used for removal of biological nitrogen and/or phosphorous has functions of: applying microorganisms which consume organic carbon as nutrients to remove BOD and/or COD-related organic materials from raw wastewater; and allowing organic nitrogen and/or ammonia to undergo nitritation and then be oxidized into nitrate-nitrogen. For this purpose, air must be sufficiently fed to the wastewater in the aeration tank and the supplied air must be homogeneously mixed with the wastewater and microorganisms, to thereby improve oxygen permeation.
Therefore, the aeration tank described above is a reactor used to purify wastewater, sewage, livestock sludge, etc., and is commonly equipped with an air diffuser at a lower portion thereof, in order to pass high oxygen concentration air through contaminants in the wastewater, thus promoting degradation of the contaminants by microorganisms and purification of the wastewater.
However, purification of highly concentrated wastewater entails a problem of decreased oxygen transfer rate to contaminants in the wastewater and, in order to solve this problem, various attempts such as increase in aeration tank capacity, additional provision of an air diffuser, use of an air diffuser to generate micro-bubbles, and so forth, have been conducted.
However, the foregoing methods to overcome decrease in oxygen transfer rate to contaminants in wastewater have been faced with tasks of increasing aeration tank capacity and/or content of dissolved oxygen in the wastewater, in turn entailing economic problems such as land acquisition costs, construction costs, energy consumption, and so forth.
Most apparatuses for purification of wastewater in the prior art have adopted a box type aeration tank equipped with an air diffuser at a lower part thereof, in which air flowing through the air diffuser is mixed with wastewater to accelerate degradation of contaminants by microorganisms, as described in Korean Laid-Open Patent Publication No. 2009-22168 (entitled “Method for treatment of livestock wastewater and apparatus therefor”), Korean Patent Publication No. 10-0709456 (entitled “Apparatus and method for treatment of wastewater treatment”), Korean Laid-Open Patent Publication No. 1998-67740 (entitled “method and apparatus for removal of nutrients in treatment of sewage and wastewater”), or the like. However, since the box type aeration tank used in such a wastewater treatment apparatus described above generally has a single structure that is not divided into multiple blocks or sections, wastewater may directly pass through the aeration tank and contact time between the wastewater and air is very short, in turn deteriorating degradation capability of contaminants in the wastewater.
Intensive and extensive studies have been conducted to solve the foregoing problem, for example; Korean Laid-Open Patent Publication No. 1999-83987, entitled “Apparatus for treatment of sewage wastewater using U shaped aeration tank,” discloses an apparatus having a ‘U’ shaped aeration tank to treat sewage wastewater, so as to increase contact time between wastewater and air. However, this U shaped aeration tank still has a single structure without compartmental blocks or sections, so that the wastewater directly passes through the aeration tank and the contact time between the wastewater and air is too short, thus entailing a problem of decreased contaminant degradation capability.